GEO600 Detector Status

Harald LückMax-Planck Institut für Gravitationsphysik

Institut für Atom- und Molekülphysik, Uni Hannover

Worldwide Interferometer Network

Laser

Optical Layout

Michelson Interferometer

Output Mode Cleaner

Mode Cleaners

600m 10 W 5 W

1 W

~ 5 kW

10 kW atBeam Splitter

~50mW

Light power (specs)

GEO 600 Sensitivity specs.

GEO 600 Sensitivity specs.

Laser

Light Power (current)

Michelson Interferometer

Output Mode Cleaner

Mode Cleaners

10W 1W

300W atBeam Splitter

2W

~10mWMode Cleaners:

Troughput 80% 72%

Finesse 2700 1900

Visibility 96% 92%

98.65%

Power Recycling Cavity:

Mode matching 97%Finesse 450Linewidth 270 Hz

Optical Layout

Main Interferometer

Mode Cleaner

Laser Bench

Output Bench

Slave

Master

Master

Slave

entrance to vacuum system

Laser SystemMaster Laser:

Nd:YAG NPRO (non-planar ring

oscillator) 800mW @ 1064 nm

Slave Laser:

Nd:YAG injection-locked ring

cavity 14 W @ 1064nm less than 5% in higher

modes

Additional Information:

Talk:Wednesday 12:40 – 13:10 hBenno Willke

Poster session:

Tuesday 20:30 – 22:00 h

GEO Triple Pendulum Suspension

Thermal Noise Issues Monolithic Suspension

Silicate (Hydroxy- Catalysis) Bonding

Weld

Length and Frequency Control

MichelsonInterferometer

Output Mode Cleaner

Laser

Mode Cleaners25 MHz13 MHz37 MHz

Laser Frequency Stabilisation:

no rigid reference cavity

laser is directly stabilised to suspended cavities

3 sequential Pound- Drever-Hall control loops

common mode of the Power-Recycled Michelson

serves as frequency reference

Mode Cleaners

Output Mode Cleaner

Michelson Length Control

MichelsonInterferometer

Laser

15 MHz

10 MHz

Differential arm length:(gravitational wave signal)

heterodyne detection Schnupp modulation

Signal-Recycling control:

separate modulation frequency

reflected beam from beam splitter AR coating

Reaction Pendulum:

3 coil-magnet actuators at intermediate mass

Electrostatic actuation on test mass bias 500V, range 0-800V=4µm

Test Mass Actuators

<10Hz

>10Hz

Alignment Control

differential wave-front sensing

spot position control

4 degrees of freedom at MC 1

+4 at MC 2+4 at MI (common mode)+2 at MI (differential mode)+2 at Signal-Recycling cavity

16 + 20 = 36

Alignment Control

Magnet/coil actuators on IM

UGF: ~10Hz

Diff. MI Fast Auto-Alignment

Output port

Reduces misalignment below 50 nrad rms

Reliable locking over long timescales. Duty cycle >95%

Output mode

Radii Of Curvature of folding mirrors do not match

East ROC: 687m

North ROC: 666m

Spec: 640m

Thermal adjustment of ROC

+-

Thermal adjustment of ROC (II)

15 W10 W

15 W20 W

15 W30 W

15 W40 W

15 W50 W

15 W50 W

15 W60 W

15 W70 W

Signal Recycling

• Mirror Reflectivity = 99%

• Coil/magnet actuation directly to mirror

• Triple pendulum suspension with reaction pendulum chain

• Tunable between 550Hz and 5kHz

• Mode-healing

2x

Signal Recycling

• Mirror Reflectivity = 99%

• Coil/magnet actuation directly to mirror

• Triple pendulum suspension with reaction pendulum chain

• Tunable between 550Hz and 5kHz

• Mode-healing

5 kHz 3 kHz 1 kHz

Sensitivity Development

Dec. 2001

Aug. 2002

Nov. 2003

Jan. 2004

78%

98.5%

95.2%

98.7%